1. Field of the Invention
The present invention relates to an IP telephone system, an IP telephone apparatus and a calling method that can transfer a file over an IP network.
2. Description of Related Art
With rapid growth of the Internet these days, an IP telephone system has drawn attention since the system allows low-rate calls to a telephone apparatus in a remote location and free calls between IP telephone apparatuses of subscribers. In the IP telephone system, a source IP telephone apparatus and a destination IP telephone apparatus perform call control using a call control protocol, such as SIP (Session Initiation Protocol). The IP telephone apparatuses then establish a voice communication between users using an information transfer protocol, such as RTP (Realtime Transport Protocol), for exchanging voice information.
Meanwhile, digital devices for capturing images, including a digital camera, have been exploding in popularity. Accordingly, data of images captured by the digital devices are sent to persons who are subjects of the images. A common way to send the image data is to attach the image data to e-mail.
ENUM (Telephone Number Mapping) has recently attracted attention as a technology that efficiently controls information handled by various communication tools, including telephones, facsimile machines, cellular phones, e-mail and the like, and that enables communication suitable to an environment of use. Based on identification numbers unique in the world represented by E.164, ENUM identifies services on the Internet using a DNS (Domain Name System). The IETF has been standardizing ENUM and discussing specifications of the protocol.
[Related Art 1] Japanese Patent Laid-open Publication 2004-48239
[Publication 1] The first report of ENUM Trial Japan issued by ENUM Trial Japan in May, 2004
Sending the image data and the like attached to e-mail, however, may require a long time to complete transmission. When transmission takes long, the size of the image data attached to e-mail is required to reduce.
Using a currently popular IP telephone system to transmit the image data and the like would benefit users. In the current IP telephone system, however, no function to transfer files of the image data and the like is generally available. Therefore, it is expected to provide an IP telephone system that can transfer image data files and the like.